If it's going to be a commuter car, and not really used for much hauling, you should consider Beetle TDIs, especially if you're going to lower/wheels/tune it. They tend to be cheaper than Golf/Jetta TDIs for being on the same chassis and having the same powertrain.
http://www.mercedesexpert.com/inventory/view/5291545?2003+Volkswagen+New+Beetle+GLS+TDI+Naples+FL
If you're kicking a mid-20MPG car out of the garage because of fuel economy, even with TDI why would you be considering AWD/4WD? It would put noticable pressure on your MPGs...